I’ve test driven a lot of vehicles over the last six months or so, spending a week with each of the best selling hybrids, as well as a handful of the smaller SUVs and a slew of small fuel-efficient vehicles. Over this time, I’ve come to realize that there’s a very simple way to increase gas mileage without spending a dime or taking undue risks. This gas saving technique is remarkably simple, yet many folks have never given it a try.
It all starts by asking yourself this basic question …
When you’re driving, what percentage of the time is your foot completely off the accelerator? To be clear: not resting on the accelerator, but resting on the carpet.
Simply put: a lazy foot wastes gas. The less time your foot currently spends off the gas pedal, the greater your potential for savings.
If your foot rests on the pedal 100% of the time, you could easily see a 25% reduction in the amount of gas you consume through the effective use of this technique.
The easiest way to see the direct results are to watch your vehicle’s real-time or “instant” mile per gallon (MPG) display, if it is so equipped. When you lift your foot off the gas, the real-time MPG numbers will skyrocket. When you reapply your foot, you can more easily modulate the pressure you exert on the pedal.
The accelerator pedal was designed over 100 years ago, and despite nifty advances like electronic drive-by-wire, remains a relatively crude way for the driver to tell the engine how much fuel to deliver. The biggest problem is that the (available) data is hidden. But just as importantly, the ankle is easily fatigued, and unless you’re Ronaldinho, can be a rather imprecise device when it comes to precisely metering fuel. (Hence the popularity of cruise control.)
The Engine Control Unit (ECU) provides a highly relevant data stream that lets you know exactly how much pressure you’re placing on the pedal. Unfortunately, this Throttle Position (TPI) data is displayed on precious few dashboards (if any). That’s not to say that you can’t easily get at the TPI. All you need to do is plug a display device like the ScanGaugeII into your (1996 or later) vehicle’s OBDII port.
I started using this feather-footed method while test driving the Toyota-technology equipped hybrids — the Ford Escape Hybrid, Nissan Altima Hybrid, Lexus 400h, Highlander Hybrid, and Camry Hybrid, and Prius — as a means to provoke the Hybrid Synergy drive systems into electric mode. After a few weeks of switching back and forth between driving hybrids and conventional vehicles, I realized that the same pulse and glide technique could yield considerable benefits no matter the method of propulsion.
A proper modern automatic transmission can allow an engine to drop RPMs in cruising mode, sometimes to near idle levels. The easiest way to see this is to lift your foot while descending a hill. Through the magic of inertia, you will maintain speed, while slashing the amount of fuel consumed.
Ecodrive.org explains the phenomena in their Golden Rules of Eco-Driving:
Petrol and diesel cars manufactured from 1990 onwards, are generally equipped with fuel injection combined with an electronic function that cuts off the engine’s fuel supply under engine braking (accelerator released and a gear engaged). The advantages of this fuel cut off function can be used by releasing the accelerator in time, for example when approaching traffic lights. This also reduces wear and tear on the brakes, reducing maintenance costs. Engine braking, not only has a positive effect on fuel consumption, but also on exhaust emissions, traffic safety, traffic flow and passenger comfort.
In case of less modern cars with a carburetor and older diesel cars (generally manufactured before 1990), it makes no difference whether you decelerate with gears engaged or disengaged, for the carburettor is a mechanical device that is not equipped with electronics to cut off fuel supply. These cars consume an equal amount of fuel under engine braking and when idling. However, releasing the accelerator in time still avoids hard braking and improves the durability of the brakes.
As your vehicle ends its decent, gently reapply throttle, while watching the real-time MPG gauge. Keep your foot as light as possible to maintain speed.
I’m working on a new video this week that will break down this technique into its basic elements. If all goes well, I’ll do this as a three camera shoot, with one camera on the floorboards, one focused on the ScanGauge, and the other on the road.
– by Daniel Gray